scholarly journals HIGH QUALITY GAN AND ALGAN LAYERS GROWN BY AMMONIA MBE WITH US GA AS SURFACTANT

2016 ◽  
Vol 2 (1) ◽  
pp. 126-129
Author(s):  
Зайцев ◽  
Sergey Zaytsev ◽  
Новиков ◽  
Sergey Novikov ◽  
Петров ◽  
...  
Keyword(s):  
Growth Rate ◽  
Substrate Temperature ◽  
Buffer Layer ◽  
Rate Constant ◽  
Growth Kinetics ◽  
Growth Rate Constant ◽  
High Quality ◽  
Mbe Growth ◽  
Surface Mobility ◽  
Aln Buffer

In this work we present the results of AlN buffer layer ammonia MBE growth for HEMT using Ga as surfactant. Key parameters that affect the growth kinetics and defects formation are efficient fluxes of precursors and surfactant as well as the substrate temperature which limits surfactant flux because of desorption Ga from the surface. In particular, addition of Ga flux equal to Al flux at substrate temperature 1150 °C keeps the growth rate constant. This approach allows to increase surface mobility of adatoms, provides quick transition to 2D–growth mode, that results in mobility increasing in GaN bulk layer as well as in heterostructures with 2DEG. In GaN/AlGaN heterostructures mobility up to 2000 cm2/Vs was achieved.

Kinetics and Mechanism of Growth of β-Solid Solution during Reaction Diffusion in Binary Titanium and Zirconium Alloy Systems

2008 ◽  
Vol 279 ◽  
pp. 117-124 ◽  
Author(s):  
G.P. Tiwari ◽  
Osamu Taguchi ◽  
Yoshiaki Iijima ◽  
G.B. Kale
Keyword(s):  
Solid Solution ◽  
Growth Rate ◽  
Rate Constant ◽  
Growth Kinetics ◽  
Zirconium Alloy ◽  
Arrhenius Plot ◽  
Reaction Diffusion ◽  
Growth Rate Constant ◽  
Satisfactory Description ◽  
Alloy Systems

High temperature beta-phase in titanium and zirconium alloy systems decomposes through an eutectoid reaction into a Ti- and Zr-rich a-solid solution and an intermetallic compound. The present paper reports the layer growth kinetics of the b-solid solution phase in elemental diffusion couples of titanium and zirconium. The growth kinetics obeys a parabolic growth law. However, the temperature dependence of the growth rate constant shows a bimodal behavior. The Arrhenius plot of the growth rate constant, which is linear at the start, becomes curved at lower temperature ranges. The deviation from the Arrhenius plot of the growth rate constant is related to the curvature in the solvus line of the b-solid solution. A theoretical model for the reaction diffusion responsible for the growth of b-solid solution is presented. The growth rate of b-phase is described by the equation 2 2 . . W k D C t b = = b D x , where k is a growth rate constant and Wb is the thickness of the b-phase formed over a period of time t, Db is the interdiffusion coefficient for the b-phase, DC is concentration range of b-phase and x is a parameter which is a function of the miscibility gaps in the phase diagram on the either side of the b-phase. The above equation provides a satisfactory description of the various aspect of the phenomenon of the growth of b-phase in Ti-and Zr-alloy systems.

scholarly journals NOVEL MATHEMATICAL MODELS FOR PREDICTION OF MICROBIAL GROWTH KINETICS AND CONTAMINANT DEGRADATION IN BIOREMEDIATION PROCESS

2016 ◽  
Vol 24 (3) ◽  
pp. 157-164 ◽  
Author(s):  
Azadeh KHOSHDEL ◽  
Behrooz MAHMOODZADEH VAZIRI
Keyword(s):  
Growth Rate ◽  
Specific Growth Rate ◽  
Rate Constant ◽  
Growth Kinetics ◽  
Microbial Growth ◽  
Specific Growth ◽  
Growth Rate Constant ◽  
Substrate Consumption ◽  
Contaminant Degradation ◽  
Microbial Growth Kinetics

Bioremediation is defined as a process, which involves decomposition of organic pollutant compounds available in soil and water resources into safe and eco-friendly materials, like water and CO2, by the microorganisms. In the present article, mathematical modeling of the bioremediation process was conducted comprehensively, and new models proposed for the microbial growth kinetics and substrate consumption (contaminant degradation). Accordingly, six kinetic models were suggested for the biomass growth and six models for the substrate consumption. Moreover, two models were considered for specific growth rate constant of the microorganisms. Then, model predictions were compared to and validated by the available experimental data in the literature. According to the obtained results, the microbial growth kinetic model, entitled as “MVKH2”, the substrate (contaminant) consumption model, entitled as “MVKH2s”, and the Aiba specific growth rate constant model had the best performance and the least error value in predicting the bioremediation process. Results achieved from this study are a promising beginning for practical and experimental works.

A RHEED Study of MBE Growth of ZnSe on GaAs (111) A-(2 × 2)

2003 ◽  
Vol 10 (04) ◽  
pp. 669-675
Author(s):  
F. S. Gard ◽  
J. D. Riley ◽  
R. Leckey ◽  
B. F. Usher
Keyword(s):  
Growth Rate ◽  
Electron Diffraction ◽  
Substrate Temperature ◽  
Three Dimensional ◽  
High Energy ◽  
Growth Mode ◽  
Two Dimensional ◽  
High Energy Electron ◽  
Mbe Growth ◽  
Atomic Flux

ZnSe epilayers have been grown under various Se/Zn atomic flux ratios in the range of 0.22–2.45 at a substrate temperature of 350°C on Zn pre-exposed GaAs (111) A surfaces. Real time reflection high energy electron diffraction (RHEED) observations have shown a transition from a two-dimensional (2D) to a three-dimensional (3D) growth mode. The transition time depends directly upon the growth rate. A detailed discussion is presented to explore the cause of this change in the growth mode.

Growth Rates of Cranes Reared in Captivity

The Auk ◽  
1986 ◽  
Vol 103 (1) ◽  
pp. 125-134 ◽  
Author(s):  
Robert E. Ricklefs ◽  
Donald F. Bruning ◽  
George W. Archibald
Keyword(s):  
Growth Rate ◽  
Incubation Period ◽  
Rate Constant ◽  
Bird Species ◽  
Growth Rate Constant ◽  
Egg Mass ◽  
In Captivity ◽  
Altricial Birds ◽  
Adult Mass ◽  
Rates Of Growth

Abstract We measured eggs, incubation periods, growth of chicks, and masses of adults of 10 species of cranes at the Bronx Zoo and the International Crane Foundation. Growth rate constants of Gompertz equations fitted to the data varied between 0.034 and 0.057/day. These values were 50-90% of those for altricial birds of comparable adult mass, and were considerably greater than those of other precocial species, such as galliforms. Rates of growth intermediate between altricial and precocial species are consistent with the fact that crane chicks, although precocial, are brooded and fed by their parents during much of the early development period. Within species, asymptote (A) and growth-rate constant (K) of the Gompertz equations were negatively correlated, owing to their inherent relationship in the curve-fitting process. Masses of chicks during the first month after hatch were unrelated to the mass asymptote, but correlated strongly with the estimated growth-rate constant. The mass of the neonate was about 60% of the fresh mass of the egg. Egg mass was unrelated to subsequent chick mass during the first month, but correlated with the mass asymptote in two species when the relationship between A and K was accounted for statistically. Egg mass also was correlated with incubation period, fledging period, and the growthrate constant in isolated instances. Growth rate and asymptote among species were inversely related, as found among large samples of diverse bird species. The size of the egg relative to the mass of the adult was related inversely to adult mass, again consistent with patterns in other groups of birds. Fledging period was related strongly to the length of the incubation period and weakly to the asymptote to the growth curve, and it was unrelated to growth-rate constant of the Gompertz equation.

Tumor regression and growth rates determined in two intramural NCI prostate cancer trials: The growth rate constant as an indicator of therapeutic efficacy.

2012 ◽  
Vol 30 (5_suppl) ◽  
pp. 133-133
Author(s):  
Bamidele Adesunloye ◽  
Wilfred Donald Stein ◽  
Julia Wilkerson ◽  
Xuan Huang ◽  
Fatima H Karzai ◽  
...  
Keyword(s):  
Growth Rate ◽  
Rate Constant ◽  
Tumor Regression ◽  
Acquired Resistance ◽  
Assessment Method ◽  
Prolonged Treatment ◽  
Growth Rate Constant ◽  
Two Phase ◽  
Phase Equation ◽  
D Values

133 Background: Like ATTP [bevacizumab + thalidomide + docetaxel + prednisone], ARTP [bevacizumab + lenalidomide + docetaxel + prednisone] is active in CRPC and in both the data suggest acquired resistance does not develop, supporting a strategy that continues therapy if tolerable. Discerning amongst new therapies in CRPC would be helped by novel assessment strategies that yield answers from smaller trials and allow comparisons across trials. We have validated a novel assessment method that quantifies tumor regression (d) and growth (g) rate constants using data obtained while pts are treated in a trial. We utilized this method to evaluate a phase II trial of ARTP in CRPC contrasting this with a previous study using thalidomide instead of lenalidomide (ATTP). Methods: Using PSA values and a two-phase mathematical equation we determined d and g. A three-phase equation was used to determine resistant fractions. Results: The median log g value with ARTP (-2.84) was statistically similar (p=0.204) to that observed with ATTP (-3.16). Both therapies had similar effects on log d (ARTP=-2.18; ATTP=-2.64; p=0.404). In a subset of pts with robust data both regimen are highly effective with only 3.01% and 5.46% of tumor resistant to ATTP and ARTP, respectively. In individual pt, statistically valid g and d values could be estimated after the fourth PSA value had been obtained, long before PSA increased - providing an early indicator of treatment failure. In most pts receiving prolonged treatment – as long as 700 d – the growth rate constant did not change, despite rising PSA values, indicating acquired resistance did not develop, and that if tolerable, therapy can be continued for longer periods of time. Conclusions: The substitution of daily thalidomide with lenalidomide 14/21 days in ARTP resulted in a combination statistically as effective as ATTP. As with ATTP majority of pts experienced marked reductions in the tumor’s g, and surprisingly in most, there was no evidence of acquired resistance, g remaining unchanged over prolonged time periods. Given the tolerability of this combination, pts with marked reductions in g may benefit from prolonged ARTP therapy.

Effect of Ag Addition on Growth of the Interfacial Intermetallic Compounds between Sn-0.7Cu Solder and Cu Substrate

2015 ◽  
Vol 815 ◽  
pp. 129-134 ◽  
Author(s):  
Xiao Chen Xie ◽  
Xiu Chen Zhao ◽  
Ying Liu ◽  
Jing Wei Cheng ◽  
Bing Zheng ◽  
...  
Keyword(s):  
Growth Rate ◽  
Intermetallic Compound ◽  
Rate Constant ◽  
Growth Rate Constant ◽  
Solder Joint Reliability ◽  
Ag Addition ◽  
Cu Substrate ◽  
Joint Reliability ◽  
Aging Properties ◽  
Interfacial Intermetallic Compounds

The effect of Ag content on the morphology of the intermetallic compound (IMC) layer at the interface between Sn-xAg-0.7Cu (x=0.0 wt.%, 0.3 wt.%, 0.8 wt.%, 3.0 wt.%) and Cu substrate has been investigated. After reflow, the slight addition of Ag element can suppress the growth of IMC. However, as the Ag content increases, the thickness of IMC is enhanced. After aging at 150°C, the IMC growth rate constant decreases with the addition of Ag. The IMC growth rate constant of Sn-3.0Ag-0.7Cu is 0.94864×10-5μm2/s, which is the lowest among these solders. As the Ag addition is 0.8wt% and 3.0wt%, the Cu3Sn growth rate constant is 0.16641×10-5μm2/s and 0.18496×10-5μm2/s, compared to the Sn-0.7Cu solder decreased 54% and 49%, respectively. As a result, the addition of Ag element improves the anti-aging properties and suppresses the growth of Cu3Sn layer, which leads to the improvement of solder joint reliability.

Optical and structural studies of high-quality bulk-like GaN grown by HVPE on a MOVPE AlN buffer layer

2006 ◽  
Vol 21 (5) ◽  
pp. 702-708 ◽  
Author(s):  
D Gogova ◽  
D Siche ◽  
R Fornari ◽  
B Monemar ◽  
P Gibart ◽  
...  
Keyword(s):  
Buffer Layer ◽  
Structural Studies ◽  
High Quality ◽  
Aln Buffer

Dynamics of Mbe Growth Surface Roughening of Ge (001) - A Stochastic Model Study

1990 ◽  
Vol 202 ◽  
Author(s):  
Venkatasubramanian R. Khoie ◽  
Rahim Khoie
Keyword(s):  
Growth Rate ◽  
Surface Roughness ◽  
Electron Diffraction ◽  
Stochastic Model ◽  
Substrate Temperature ◽  
Growth Temperature ◽  
Average Surface Roughness ◽  
Mbe Growth ◽  
Average Surface ◽  
Kinetic Roughening

ABSTRACTA stochastic model for the MBE growth of Ge is developed based on the master equation approach with solid-on-solid restriction and quasi-chemical approximation. The surface kinetic processes included are: adsorption, evaporation and intralayer and interlayer migrations. The growth rate, the average surface roughness and the average intensity of reflection high energy electron diffraction (RHEED) (using kinematical theory of electron diffraction’ were obtained for the MBE growth of Ge with the temperature in the range 100-500°C and a typical flux of 1 Å/sec. The average surface roughness and the growth rate are found to be independent of substrate temperature below 150°C and above 400°C. In the intermediate temperature range, the growth rate increases and the surface roughness decreases with increasing temperature. The kinetic roughening temperature above which a smooth surface remains smooth, is identified from the temperature depen-dance of the average surface roughness and RHEED intensity, as 400°C. The temperature dependance of the average RHEED intensity and the kinetic roughening temperature obtained from this study compare favorably with the experimental results. At low substrate temperature, the surface migration rate is negligible irrespective of the temperature and therefore, the surface roughness and the growth rate become independent of the growth temperature. At high substrate temperatures, the surface roughness and the growth rate attain the limiting values for the flux chosen, owing to the saturation of the available sites for the interlayer migration process. Thus, these parameters become independent of the growth temperature.

Simulations of molecular beam epitaxy growth of GaAs

2000 ◽  
Vol 648 ◽  
Author(s):  
Z. Zhang ◽  
B. G. Orr
Keyword(s):  
Molecular Beam Epitaxy ◽  
Substrate Temperature ◽  
Numerical Simulations ◽  
Molecular Beam ◽  
High Surface ◽  
Molecular Beam Epitaxy Growth ◽  
Smooth Surfaces ◽  
Mbe Growth ◽  
Surface Mobility ◽  
Key Aspects

AbstractNumerical simulations have been performed for generic III-V MBE growth. The key aspects of the simulation include two deposited species one volatile and the second with high surface mobility. Simulations reproduce the experimentally observed adatom concentrations for GaAs and show that smooth surfaces are produced for films deposited with a substrate temperature in a crossover regime between kinetically limited and entropically roughened growth.

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